Multi-layer golf ball

ABSTRACT

Disclosed herein is a golf ball with a multi-layer cover. The golf ball has a core, an inner cover layer, an intermediate cover layer, and an outer cover layer, each cover layer having a different hardness than each adjacent cover layer. The sum of the thickness of the inner cover layer, intermediate cover layer and outer cover layer is 0.05-0.50 inches. A method for making the golf ball also is disclosed.

RELATED APPLICATIONS

This application is a division of U.S. Application Ser. No. 09/008,802filed Jan. 20, 1998, now U.S. Pat. No. 6,117,125, which, in turn, is acontinuation-in-part of U.S. application Ser. No. 08/490,963 filed Jun.15, 1995, now U.S. Pat. No. 6,042,488, U.S. application Ser. No.08/495,062 filed Jun. 26, 1995, now U.S. Pat. No. 5,830,087, andProvisional U.S. application No. 60/042,119 filed Mar. 28, 1997.

FIELD OF THE INVENTION

The present invention generally relates to golf balls, and moreparticularly to a golf ball having a cover which includes at least threelayers.

BACKGROUND OF THE INVENTION

Golf balls traditionally have been categorized in three differentgroups, namely as one-piece, two-piece and three-piece balls.Conventional two-piece golf balls include a solid resilient core havinga cover of a different type of material molded thereon. Three-piece golfballs traditionally have included a liquid or solid center, elastomericwinding around the center, and a molded cover. Solid cores of both twoand three-piece balls often are made of polybutadiene and the moldedcovers generally are made of natural balata, synthetic balata, orionomeric resins.

lonomeric resins are polymers containing interchain ionic bonding. As aresult of their toughness, durability and flight characteristics,various ionomeric resins sold by E.I. DuPont de Nemours & Company underthe trademark "Surlyn®" and by the Exxon Corporation (see U.S. Pat. No.4,911,451) under the trademark "Escor®" and the trade name "lotek", havebecome the materials of choice for the construction of golf ball coversover the traditional "balata" (transpolyisoprene, natural or synthetic)rubbers. The softer balata covers, although exhibiting enhancedplayability properties, lack the durability (cut and abrasionresistance, fatigue endurance, etc.) properties required for repetitiveplay.

lonomeric resins are generally ionic copolymers of an olefin, such asethylene, and a metal salt of an unsaturated carboxylic acid, such asacrylic acid, methacrylic acid or maleic acid. Metal ions, such assodium or zinc, are used to neutralize some portion of the acidic groupin the copolymer, resulting in a thermoplastic elastomer exhibitingenhanced properties, i.e., durability, etc., for golf ball coverconstruction over balata.

While there are currently more than fifty (50) commercial grades ofionomers available from Exxon and DuPont, with a wide range ofproperties which vary according to the type and amount of metal cations,molecular weight, composition of the base resin (i.e., relative contentof ethylene and methacrylic and/or acrylic acid groups) and additiveingredients such as reinforcement agents, etc., a great deal of researchcontinues in order to develop a golf ball cover composition exhibitingthe desired combination of playability properties.

Golf balls are typically described in terms of their size, weight,composition, dimple pattern, compression, hardness, durability, spinrate, and coefficient of restitution (COR). One way to measure the CORof a golf ball is to propel the ball at a given speed against a hardmassive surface, and to measure its incoming and outgoing velocity. TheCOR is the ratio of the outgoing velocity to the incoming velocity andis expressed as a decimal between zero and one.

There is no United States Golf Association limit on the COR of a golfball but the initial velocity of the golf ball must not exceed 250±5ft/second. As a result, the industry goal for initial velocity is 255ft/second, and the industry strives to maximize the COR withoutviolating this limit.

U.S. Pat. Nos. 4,431,193 and 4,919,434 disclose golf balls withmulti-layer covers. U.S. Pat. No. 4,431,193 discloses a multi-layer ballwith a hard inner cover layer and a soft outer cover layer. U.S. Pat.No. 4,919,434 discloses a golf ball with a 0.4-2.2 mm thick cover madefrom two thermoplastic cover layers. U.S. Pat. No. 5,273,286 discloses agolf ball with a multi-layer core. The golf ball disclosed therein hasan inner core, a shell surrounding the inner core, an outer core, and acover.

SUMMARY OF THE INVENTION

An object of the invention is to provide a golf ball for a low handicapplayer which has a favorable combination of spin and feel.

Another object of the invention is to provide a golf ball for a highhandicap player which has a favorable combination of spin and feel.

A further object of the invention is to provide a method of makingmulti-layer golf balls in which the characteristics of spin and feel canbe carefully controlled to result in a desired combination of theseproperties.

Other objects of the invention will be in part obvious and in partpointed out more in detail hereinafter.

A preferred form of the invention is a golf ball comprising a solid orwound core, an inner cover layer formed around the core, an intermediatecover layer formed around the inner cover layer, and an outer coverlayer formed around the intermediate cover layer, each cover layerhaving a different Shore D hardness than each adjacent cover layer. Theouter cover layer preferably comprises ionomer.

The invention in another preferred form is a golf ball comprising asolid or wound core, an inner cover layer formed around the core, theinner cover layer having a Shore D hardness of at least 62, preferablyin the range of 62-90, an intermediate cover layer formed around theinner cover layer, and an outer cover layer formed around theintermediate cover layer, each cover layer having a different Shore Dhardness than each adjacent cover layer.

In a particularly preferred form of the invention, the intermediatecover layer is softer than the inner and outer cover layers. In anotherembodiment, the intermediate cover layer is harder than the outer coverlayer and softer than the inner cover layer. In yet another embodiment,the intermediate cover layer is softer than the outer cover layer andharder than the inner cover layer. In a fourth embodiment, theintermediate cover layer is harder than the inner and outer coverlayers. Each of the inner, intermediate and outer cover layerspreferably has a thickness of 0.01-0.20 inches, and more preferably0.025-0.15 inches.

The outer cover layer preferably comprises ionomer. The inner andintermediate cover layers preferably are thermoplastic. In particularlypreferred forms of the invention, the inner cover layer and/orintermediate cover layer also comprise ionomer.

The inner, intermediate and/or outer cover layers may contain at leastone part by weight of a filler based upon 100 parts of resincomposition. If filler is used, it preferably is included in an amountof at least 5 parts by weight based upon 100 parts by weight of resincomposition. The filler preferably is selected from the group consistingof precipitated hydrated sirica, clay, talc, asbestos, glass, aramidfibers, mica, calcium metasilicate, barium sulfate, zinc sulfide,lithopone, silicon carbide, silicates, diatomaceous earth, carbonates,metals, metal alloys, metal oxides, metal stearates, particulatecarbonaceous materials, cotton flock, cellulose flock, leather fiber,micro balloons and combinations thereof.

In one form of the invention, at least one of the inner cover layer andintermediate cover layer comprises a non-ionomeric polyolefin material.This material preferably includes at least one member selected from thegroup consisting of low density polyethylene, linear low densitypolyethylene, high density polyethylene, polypropylene, rubber-toughenedolefin polymers, acid copolymers which do not become part of anionomeric copolymer, plastomers including metallocene catalyzedpolyolefins, flexomers, styrene/butadienelstyrene block copolymers,styrene/ethylene-butylene/styrene block copolymers, dynamicallyvulcanized elastomers, ethylene vinyl acetates, ethylene methylacrylates, polyvinyl chloride resins, polyamides, amide-esterelastomers, graft copolymers of ionomer and polyamide, crosslinkedtranspolyisoprene blends, thermoplastic block polyesters, thermoplasticpolyurethanes and thermosetting polyurethanes.

A further preferred form of the invention is a golf ball comprising asolid core, an inner cover layer, an intermediate cover layer and anouter cover layer. The inner cover layer comprises at least one memberselected from the group consisting of ionomers, thermoplastic elastomersand non-ionomeric polyolefins. The intermediate cover layer comprises atleast one member selected from the group consisting of ionomers,thermoplastic elastomers and non-ionomeric polyolefins. The outer coverlayer comprises at least one member selected from the group consistingof ionomers, thermoplastic elastomers and non-ionomeric polyolefins andpreferably comprises an ionomer. Each of the inner cover layer, theintermediate cover layer and the outer cover layer is a separate anddistinct layer.

In the golf ball of the invention, at least one of the inner cover layerand the intermediate cover layer can be foamed. Furthermore, the outercover layer can be foamed as long as molding does not result inunacceptable surface imperfections on the ball.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and thearticle possessing the features, properties, and the relation ofelements exemplified in the following detailed disclosure.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a cross-sectional view of a first embodiment of a golf ballaccording to the invention.

FIG. 2 shows a cross-sectional view of a second embodiment of a golfball according to the invention.

FIG. 3 shows a cross-sectional view of a third embodiment of a golf ballaccording to the invention.

FIG. 4 shows a cross-sectional view of a fourth embodiment of a golfball according to the invention.

FIG. 5 shows a cross-sectional view of a fifth embodiment of a golf ballaccording to the invention.

FIG. 6 shows a cross-sectional view of a sixth embodiment of a golf ballaccording to the invention.

FIG. 7 shows a cross-sectional view of a seventh embodiment of a golfball according to the invention.

FIG. 8 shows a cross-sectional view of an eighth embodiment of a golfball according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The golf ball according to the invention has a central core and a thickcover which includes at least three separate and distinct layers. Theinner cover layer preferably is formed from a thermoplastic material.The intermediate cover layer also preferably is formed from athermoplastic material. The outer cover layer preferably is formed froma thermoplastic material and more preferably is ionomeric. "Separate anddistinct" layers are layers with a different Shore D hardness than anyadjacent layer and in which each layer is chemically distinguishablefrom any adjacent layer. Moreover, if a layer is foamed giving rise to asolid skin surface and cellular inner structure, this is still deemed asingle layer and the hardness is defined as that of the unfoamed, solidmaterial comprising that layer.

In a first preferred embodiment of the invention, the inner and outercover layers are hard and the intermediate cover layer is softer thanthe inner and outer cover layers. This type of construction results in agolf ball having relatively low spin rates for good distance andaccuracy, and a relatively soft feel, the soft intermediate layerproviding added flexibility to an otherwise very rigid cover.

In a second preferred embodiment, the inner and outer cover layers aresoft and the intermediate cover layer is harder than the inner and outercover layers. This type of golf ball is useful when high spin on shortiron shots, but lower spin on tee shots is desired. This constructionalso gives the softest compression for a very soft feel.

In a third preferred embodiment, the inner cover layer is hard, theouter cover layer is soft, and the intermediate cover layer has anintermediate hardness. This construction is useful to form a golf ballhaving very high spin rates for maximizing the ability of a golfer tostop a ball precisely, minimizing roll.

In a fourth preferred embodiment, the inner cover layer is soft, theouter cover layer is hard, and the intermediate cover layer hasintermediate hardness. This embodiment is useful when a good balance ofrelatively low spin, yet soft feel is desirable.

In a preferred form of the invention, the Shore D hardness of each coverlayer is at least 3 points, and even more preferably is at least 5points different than the Shore D hardness of each adjacent cover layer.

Referring now to FIG. 1, a golf ball according to a first embodiment ofthe invention is shown and is designated as 9. The ball preferably has adiameter of at least 1.68 inches. The invention is particularly usefulwith golf balls having a diameter of 1.70 inches or more.

The golf ball 9 includes a central solid core 10 and a multi-layer cover12. The multi-layer cover includes an inner cover layer 14, anintermediate cover layer 15, and an outer cover layer 16 with dimples18. The inner cover layer 14 has a Shore D hardness¹ in the range of60-80, and more preferably 62-80. The intermediate cover layer 1 5 has aShore D hardness in the range of 10-55 and more preferably 30-50. Theinner and intermediate cover layers preferably are formed from ionomericor non-ionomeric polyolefin material. The outer cover layer 16preferably comprises ionomer and has a Shore D hardness in the range of60-80.

Referring to FIG. 2, a golf ball according to a second embodiment of theinvention is shown and is designated as 19. The ball preferably has adiameter of at least 1.68 inches. The ball includes a central solid core20 and a multi-layer cover 22. The multi-layer cover includes a softinner cover layer 24 having a Shore D hardness in the range of 10-55 andmore preferably 30-50, a hard intermediate cover

Referring now to FIG. 3, a third embodiment of a golf ball according tothe invention is designated as 29. The golf ball includes a centralsolid core 30 and a multi-layer cover 32. The multi-layer cover 10includes a hard inner cover layer 34 having a Shore D hardness of 60-80,and more preferably 62-80, an intermediate cover layer 35 having a ShoreD hardness of 50-65, and an outer cover layer 36 with dimples 38. Theouter cover layer has a Shore D hardness of 10-55 and more preferably30-50. The inner cover layer 34 and intermediate cover layer 35preferably comprise an ionomeric or non-ionomeric polyolefin material.The outer cover layer 36 preferably comprises ionomer.

Referring now to FIG. 4, a golf ball according to a fourth embodiment ofthe invention is shown and is designated as 39. The ball includes acentral solid core 40 and a multi-layer cover 42. The multi-layer coverincludes an inner cover layer 44 with a Shore D hardness of 10-55 andmore preferably 30-50, an intermediate cover layer 45 with a Shore Dhardness of 50-65, and an outer cover layer 46 with dimples 48. Theouter cover layer has a Shore D hardness of 60-80, and more preferably62-80. The inner and intermediate cover layers 44 and 45 preferablycomprise an ionomeric or non-ionomeric polyolefin material. The outercover layer 46 preferably comprises ionomer.

Referring now to FIG. 5, a golf ball according to a fifth embodiment ofthe invention is shown and is designated as 49. The ball includes acentral solid core 50 and a multi-layer cover 52. The multi-layer coverincludes an inner cover layer 54 with a Shore D hardness of 60-80, andmore preferably 62-80, an intermediate cover layer 55 with a Shore Dhardness of 10-55 and more preferably 30-50, and an outer cover layer 56with dimples 58. The outer cover layer has a Shore D hardness of 50-65.The inner and intermediate cover layers 54 and 55 preferably comprise anionomeric or non-ionomeric polyolefin material. The outer cover layer 56preferably comprises ionomer.

Referring now to FIG. 6, a golf ball according to a sixth embodiment ofthe invention is shown and is designated as 59. The ball includes acentral solid core 60 and a multi-layer cover 62. The multi-layer coverincludes an inner cover layer 64 with a Shore D hardness of 50-65, anintermediate cover layer 65 with a Shore D hardness of 10-55 and morepreferably 30-50, and an outer cover layer 66 with dimples 68. The outercover layer has a Shore D hardness of 60-80, and more preferably 62-80.The inner and intermediate cover layers 64 and 65 preferably comprise anionomeric or non-ionomeric polyolefin material. The outer cover layer 66preferably comprises ionomer.

Referring now to FIG. 7, a golf ball according to a seventh embodimentof the invention is shown and is designated as 69. The ball includes acentral solid core 70 and a multi-layer cover 72. The multi-layer coverincludes an inner cover layer 74 with a Shore D hardness of 10-55 andmore preferably 30-50, an intermediate cover layer 75 with a Shore Dhardness of 60-80, and more preferably 62-80, and an outer cover layer76 with dimples 78. The outer cover layer has a Shore D hardness of50-65. The inner and intermediate cover layers 74 and 75 preferablycomprise an ionomeric or non-ionomeric polyolefin material. The outercover layer 76 preferably comprises ionomer.

Referring now to FIG. 8, a golf ball according to an eighth embodimentof the invention is shown and is designated as 79. The ball includes acentral solid core 80 and a multi-layer cover 82. The multi-layer coverincludes an inner cover layer 84 with a Shore D hardness of 50-65, anintermediate cover layer 85 with a Shore D hardness of 60-80 and morepreferably 62-80, and an outer cover layer 86 with dimples 88. The outercover layer has a Shore D hardness of 10-55 and more preferably 30-50.The inner and intermediate cover layers 84 and 85 preferably comprise anionomeric or non-ionomeric polyolefin material. The outer cover layer 86preferably comprises ionomer.

For each of the embodiments shown in FIGS. 1-8, each cover layerpreferably has a Shore D hardness which is at least 3 points, and morepreferably at least 5 points, harder or softer than the Shore D hardnessof each adjacent cover layer. Preferably each layer has a differentchemical composition than each adjacent cover layer.

As indicated above, the cover layers preferably are formed from ionomer.In a preferred form of the invention, soft cover layers, i.e. those witha Shore D hardness of 10-55 and more preferably 30-50, comprise anionomer with an average wt % acid content of about 15 or less which isat least 10% neutralized. More specifically, the soft cover layerstypically constitute a blend of two types of ionomers in which onecomponent of the blend is an ethylene-acrylic acid orethylene-methacrylic acid copolymer containing ≧15 wt % acid groupswhich are at least partially neutralized with a cation, and the othertype of ionomer is a terpolymer of ethylene, acrylic acid or methacrylicacid and a softening termonomer such as butyl acrylate or methylacrylate, resulting in an overall wt % acid content of about 15 or less.Non-limiting examples of suitable blends are described in U.S. Pat. Nos.4,884,814 and 5,120,791, both of which are incorporated herein byreference. In a particularly preferred form of the invention the softcover layer is comprised of ≧75 wt % terpolymer type ionomer.

The cover layers of intermediate hardness, e.g., those with a Shore Dhardness of 50-65, preferably are made from the same types of materialsas are used for the soft cover layers. It is particularly preferred touse blends of about 25-75 wt % copolymer ionomer with about 75-25 wt %terpolymer type ionomers.

The hard ionomeric cover layer or layers can contain a single type ofionomer or a blend of two or more types of ionomers. Furthermore, ahardening and/or softening modifier can be added. In a particularlypreferred form of the invention, the hard cover layer or layers containone or more ionomers having at least 16 weight % acid groups, which areat least partially neutralized.

Each of the three cover layers can be foamed or unfoamed. Preferably,each layer is unfoamed. A foamed layer has a lower density than anunfoamed layer, thereby affecting the weight distribution and moment ofinertia. Typically, the melt index is increased by foaming. The use of afoamed cover layer results in the need to increase the weight of thecore of the ball, thereby allowing for easier initiation of spin to aball, particularly on short shots. This may partially compensate for alow spin rate on a hard covered ball, particularly in the case of aplayer who does not strike the ball at a fast swing speed. A foamedlayer generally has a lower modulus and thus increased flexibility.Typically, a foamed layer is formed by adding a small amount of achemical blowing agent to the cover material prior to molding. Theblowing agent is selected such that it will release gas at the moldingtemperature for the cover layer.

Non-limiting examples of materials which are suitable to form the outercover layer of the golf ball are ionomer, a metallocene catalyzedpolyolefin such as EXACT, INSITE, AFFINITY, or ENGAGE which preferablyis crosslinked, polyamides, amide-ester elastomer, or graft copolymer ofionomer and polyamide such as CAPRON, ZYTEL, ZYTEL FN, PEBAX, etc., acrosslinked transpolyisoprene blend, a thermoplastic block polyestersuch as HYTREL, or a thermoplastic or thermosetting polyurethane, suchas Estane® polyurethanes, including Estane® X-4517.

The inner and intermediate cover layers can be made of any of thematerials listed in the previous paragraph as being useful for formingan outer cover layer. Furthermore, the inner and intermediate coverlayers can be formed from a number of other non-ionomeric thermoplasticsand thermosets. For example, lower cost polyolefins and thermoplasticelastomers can be used. Non-limiting examples of suitable non-ionomericpolyolefin materials include low density polyethylene, linear lowdensity polyethylene, high density polyethylene, polypropylene,rubber-toughened olefin polymers, acid copolymers which do not becomepart of an ionomeric copolymer when used in the inner cover layer, suchas PRIMACOR, NUCREL, ESCOR and ATX, plastomers and flexomers,thermoplastic elastomers such as styrene/butadiene/styrene (SBS) orstyrene/ethylene-butylene/styrene (SEBS) block copolymers, includingKraton® (Shell), dynamically vulcanized elastomers such as Santoprene®(Monsanto), ethylene vinyl acetates such as Elvax® (DuPont), ethylenemethyl acrylates such as Optema® (Exxon), polyvinyl chloride resins, andother elastomeric materials may be used. Mixtures, blends, or alloysinvolving the materials described above can be used. It is desirablethat the polyolefin be a tough, low density material. The non-ionomericpolyolefins can be mixed with ionomers.

The inner, intermediate and outer cover layers optionally may includeprocessing aids, release agents and/or diluents. Another useful materialfor the inner and/or intermediate cover layers is a natural rubber latex(prevulcanized) which has a tensile strength of 4,000-5,000 psi, highresilience, good scuff resistance, a Shore D hardness of less than andan elongation of >500%.

As indicated above, the inner, intermediate and outer cover layers maycontain plastomer. The plastomer preferably either is crosslinked or isblended with an ionomer or other compatible material. Plastomers areolefin copolymers with a uniform, narrow molecular weight distribution,a high comonomer content, and an even distribution of comonomers. Themolecular weight distribution of the plastomers generally is about1.5-4, preferably 1.5-3.5 and more preferably 1.5-2.4. The density istypically in the range of 0.85-0.97 if unfoamed and 0.10-0.90 if foamed.The comonomer content typically is in the range of 1-32%, and preferably2-20%. The composition distribution breadth index generally is greaterthan 30%, preferably is at least 45%, and more preferably is at least50%.

The term "copolymer" includes (1) copolymers having two types ofmonomers which are polymerized together, (2) terpolymers (which areformed by the polymerization of three types of monomers), and (3)copolymers which are formed by the polymerization of more than threetypes of monomers. The compositions further may include additives andfillers as well as a co-agent for use with a curing agent to aid incrosslinking the plastomer or to improve processability.

The "composition distribution breadth index" (CDBI) is defined as theweight percent of the copolymer molecules which have a comonomer contentwithin 50 percent of the median total molar comonomer content.

Plastomers are polyolefin copolymers developed using metallocenesingle-site catalyst technology. Plastomers exhibit both thermoplasticand elastomeric characteristics. Plastomers generally contain up toabout 32 wt % comonomer. Plastomers which are useful in making golfballs include but are not limited to ethylene-butene copolymers,ethylene-octene copolymers, ethylene-hexene copolymers, andethylene-hexene-butene terpolymers, as well as mixtures thereof.

The plastomers employed in the invention preferably are formed by asingle-site metallocene catalyst such as those disclosed in EP 29368,U.S. Pat. No. 4,752,597, U.S. Pat. No. 4,808,561, and U.S. Pat. No.4,937,299, the teachings of which are incorporated herein by reference.As is known in the art, plastomers can be produced by metallocenecatalysis using a high pressure process by polymerizing ethylene incombination with other monomers such as butene-1, hexene-1, octene-1 and4-methyl-1-pentene in the presence of catalyst system comprising acyclopentadienyl-transition metal compound and an alumoxane.

EXACT™ plastomers (Exxon Chemical Co., Houston, Tex.) aremetallocene-catalyzed polyolefins. This family of plastomers has adensity of 0.87-0.915 g/cc, melting points in the range of 140-220° F.,Shore D hardness in the range of 20-50 (measured generally in accordancewith ASTM D-2240, but measured on the curved surface of the inner coverlayer), flexural modulus in the range of 2-15 k.p.s.i., tensile strengthof 1600-4000 p.s.i., excellent thermal stability, and very good elasticrecovery. One of these materials, known as EXACT™ 4049, is a butenecopolymer with a comonomer content of less than 28% and a polymerdensity of 0.873 g/cc. The properties of EXACT™ 4049 are shown on Table1 below:

                  TABLE 1                                                         ______________________________________                                        Polymer Properties                                                                           Typical Values.sup.1                                                                        ASTM Method                                      ______________________________________                                        Melt flow index                                                                              4.5 dg/min    D-1238 (E)                                       Density        0.873 g/cm.sup.3                                                                            D-792                                            Elastomer Properties.sup.2                                                    Hardness       72 Shore A    D-2240                                                          20 Shore D                                                     Ultimate Tensile.sup.3, Die D                                                                900 p.s.i. (6.4 MPa)                                                                        D-412                                            Tensile Modulus                                                               @ 100% elongation                                                                            280 p.s.i. (2 MPa)                                                                          D-412                                            @ 300% elongation                                                                            350 p.s.i. (2.4 MPa)                                           Ultimate Elongation                                                                          2000%         D-412                                            Brittleness Temperature                                                                      ←112° F. (←80° C.)                                                  D-746                                            Vicat Softening Point, 200 g                                                                 130° F. (55° C.)                                                              D-1525                                           Mooney Viscosity                                                                             6.5 Torque Units                                                                            D-1646                                           (1 + 4 @ 125° C.)                                                      ______________________________________                                         .sup.1 Values are typical and are not to be interpreted as specifications     .sup.2 Compression molded specimens.                                          .sup.3 Tensile properties determined using a type D die & a crosshead         speed of 20 in/min.                                                      

This material has been found to be particularly useful in forming theinner cover layer 14.

Other non-limiting examples of EXACT plastomers which are useful in theinvention include linear ethylene-butene copolymers such as EXACT 3024having a density of about 0.905 gms/cc (ASTM D-1505) and a melt flowindex of about 4.5 g/10 min. (ASTM D-2839); EXACT 3025 having a densityof about 0.910 gms/cc (ASTM D-1505) and a melt flow index of about 1.2g/10min. (ASTM D-2839); EXACT 3027 having a density of about 0.900gms/cc (ASTM D-1505) and a melt flow index of about 3.5 g/10 min. (ASTMD-2839); and EXACT 4011 having a density of about 0.887 gms/cc (ASTMD-1505) and a melt flow index of about 2.2 g/l 10 min. (ASTM D-2839);and ethylene-hexene copolymers such as EXACT 3031 having a density ofabout 0.900 gms/cc (ASTM D-1505) and a melt flow index of about 3.5 g/10min. (ASTM D-2839). Other non-limiting examples of useful EXACTplastomers are EXACT 4005 and EXACT 5010. Terpolymers of e.g. ethylene,butene and hexene also can be used. All of the above EXACT seriesplastomers are available from EXXON Chemical Co.

Similar materials sold by Dow Chemical Co. as INSITE® technology underthe AFFINITY® and ENGAGE® trademarks also can be used.

EXACT plastomers typically have a molecular weight distribution (M_(w)/M_(n)) of about 1.5. to 2.4, where M_(w) is weight average molecularweight and M_(n) is number average molecular weight, a molecular weightof about 5,000 to about 50,000, preferably about 20,000 to about 1530,000, and a melt flow index above about 0.50 g/10 mins, preferablyabout 1-10 g/10 mins as determined by ASTM D-1238, condition E.

Plastomers which may be employed in the invention include copolymers ofethylene and at least one C₃ -C₂₀ α-olefin, preferably a C₄ -C₈ α-olefinpresent in an amount of about 5 to about 32 mole %, preferably about 7to about 22 mole %, more preferably about 9-18 mole %. These plastomersare believed to have a composition distribution breadth index of about45% or more.

Plastomers such as those sold by Dow Chemical Co. under the tradenameENGAGE are believed to be produced in accordance with U.S. Pat. No.5,272,236, the teachings of which are incorporated herein in theirentirety by reference. These plastomers are substantially linearpolymers having a density of about 0.85 gms/cc to about 0.97 g/ccmeasured in accordance with ASTM D-792, a melt flow index ("MI") ofabout 0.01 gms/10 minutes to about 1000 grams/10 minutes, a melt flowratio (I₁₀ /I₂) of about 7 to about 20, where I₁₀ is measured inaccordance with ASTM D-1238 (190/10) and I₂ is measured in accordancewith ASTM D-1238 (190/2.16), and a molecular weight distribution M_(w)/M_(n) which preferably is less than 5, and more preferably is less thanabout 3.5 and most preferably is from about 1.5 to about 5 2.5. Theseplastomers include homopolymers of C₂ -C₂₀ olefins such as ethylene,propylene, 4-methyl-1-pentene, and the like, or they can beinterpolymers of ethylene with at least one C₃ -C₂₀ α-olefin and/or C₂-C₂₀ acetylenically unsaturated monomer and/or C₄ -C₁₈ diolefins. Theseplastomers generally have a polymer backbone that is eitherunsubstituted or substituted with up to 3 long chain branches/1000carbons. As used herein, long chain branching means a chain length of atleast about 6 carbons, above which the length cannot be distinguishedusing ¹³ C nuclear magnetic resonance spectroscopy. The preferred ENGAGEplastomers are characterized by a saturated ethylene-octene backbone, anarrow molecular weight distribution M_(w) /M_(n) of about 2, and anarrow level of crystallinity. These plastomers also are compatible withpigments, brightening agents, fillers such as those described above, aswell as with plasticizers such as paraffinic process oil and naphthenicprocess oil. Other commercially available plastomers may be useful inthe invention, including those manufactured by Mitsui.

The molecular weight distribution, (M_(w) /M_(n)), of plastomers made inaccordance with U.S. Pat. No. 5,272,236 most preferably is about 2.0.Non-limiting examples of these plastomers include ENGAGE CL 8001 havinga density of about 0.868 gms/cc, a melt flow index of about 0.5 g/10mins, and a Shore A hardness of about 75; ENGAGE CL 8002 having adensity of about 0.87 gms/cc, a melt flow index of about 1 gms/10 min,Shore A hardness of about 75; ENGAGE CL 8003 having a density of about0.885 gms/cc, a melt flow index of about 1.0 gms/10 min, and a Shore Ahardness of about 86; ENGAGE EG 8100 having a density of about 0.87gms/cc, a melt flow index of about 1gms/10 min., and a Shore A hardnessof about 87; ENGAGE 8150 having a density of about 0.868 gms/cc, a meltflow index of about 0.5 gms/10 min, and a Shore A hardness of about 75;ENGAGE 8200 having a density of about 0.87 gms/cc, a melt flow index ofabout 5 g/10 min., and a Shore A hardness of about 75; and ENGAGE EP8500 having a density of about 0.87 gms/cc, a melt flow index of about 5g/10 min., and a Shore A hardness of about 75.

In a particularly preferred form of the invention, at least one of theinner, intermediate and outer cover layers contains at least one part byweight of a filler based upon 100 parts by weight of the resincomposition. The filler preferably is used to adjust the density, flexmodulus, mold release, and/or melt flow index of the cover layer. Morepreferably, at least when the filler is for adjustment of density orflex modulus, it is present in an amount of at least five parts byweight based upon 100 parts by weight of the resin composition. Withsome fillers, up to about 200 parts by weight probably can be used.

A density adjusting filler according to the invention preferably is afiller which has a specific gravity which is at least 0.05 higher orlower and more preferably at least 0.1 higher or lower than the specificgravity of the resin composition. Particularly preferred densityadjusting fillers have specific gravities which are higher than thespecific gravity of the resin composition by 0.2 or more, even morepreferably by 2.0 or more.

A flex modulus adjusting filler according to the invention is a fillerwhich, when used in an amount of e.g. 1-100 parts by weight based upon100 parts by weight of resin composition, will raise or lower the flexmodulus (ASTM D-790) of the resin composition by at least 1% andpreferably at least 5% as compared to the flex modulus of the resincomposition without the inclusion of the flex modulus adjusting filler.

A mold release adjusting filler is a filler which allows for easierremoval of part from mold, and eliminates or reduces the need forexternal release agents which otherwise could be applied to the mold. Amold release adjusting filler typically is used in an amount of up toabout 2 wt % based upon the total weight of the cover layer.

A melt flow index adjusting filler is a filler which increases ordecreases the melt flow, or ease of processing of the composition.

The cover layers and core may contain coupling agents that increaseadhesion of materials within a particular layer e.g. to couple a fillerto a resin composition, or between adjacent layers. Non-limitingexamples of coupling agents include titanates, zirconates and silanes.Coupling agents typically are used in amounts of 0.1-2 wt % based uponthe total weight of the composition in which the coupling agent isincluded.

A density adjusting filler is used to control the moment of inertia, andthus the initial spin rate of the ball and spin decay. The addition inone or more of the cover layers, and particularly in the outer coverlayer, of a filler with a lower specific gravity than the resincomposition results in a decrease in moment of inertia and a higherinitial spin rate than would result if no filler were used. The additionin one or more of the cover layers, and particularly in the outer coverlayer, of a filler with a higher specific gravity than the resincomposition results in an increase in moment of inertia and a lowerinitial spin rate. High specific gravity fillers are preferred as lessvolume is used to achieve the desired inner cover total weight.Nonreinforcing fillers are also preferred as they have minimal effect onCOR. Preferably, the filler does not chemically react with the resincomposition to a substantial degree, although some reaction may occurwhen, for example, zinc oxide is used in a cover layer which containssome ionomer.

The density-increasing fillers for use in the invention preferably havea specific gravity in the range of 1.0-20. The density-reducing fillersfor use in the invention preferably have a specific gravity of 0.06-1.4,and more preferably 0.06-0.90. The flex modulus increasing fillers havea reinforcing or stiffening effect due to their morphology, theirinteraction with the resin, or their inherent physical properties. Theflex modulus reducing fillers have an opposite effect due to theirrelatively flexible properties compared to the matrix resin. The meltflow index increasing fillers have a flow enhancing effect due to theirrelatively high melt flow versus the matrix. The melt flow indexdecreasing fillers have an opposite effect due to their relatively lowmelt flow index versus the matrix.

Fillers which may be employed in the inner, intermediate and outer coverlayers may be or are typically in a finely divided form, for example, ina size generally less than about 20 mesh, preferably less than about 100mesh U.S. standard size, except for fibers and flock, which aregenerally elongated. Flock and fiber sizes should be small enough tofacilitate processing. Filler particle size will depend upon desiredeffect, cost, ease of addition, and dusting considerations. The fillerpreferably is selected from the group consisting of precipitatedhydrated silica, clay, talc, asbestos, glass fibers, aramid fibers,mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone,silicates, silicon carbide, diatomaceous earth, polyvinyl chloride,carbonates, metals, metal alloys, tungsten carbide, metal oxides, metalstearates, particulate carbonaceous materials, micro balloons, andcombinations thereof. Non-limiting examples of suitable fillers, theirdensities, and their preferred uses are as follows:

                  TABLE 2                                                         ______________________________________                                        Filler Type         Spec. Grav.                                                                             Comments                                        ______________________________________                                        Precipitated hydrated silica                                                                      2.0       1, 2                                            Clay                2.62      1, 2                                            Talc                2.85      1, 2                                            Asbestos            2.5       1, 2                                            Glass fibers        2.55      1, 2                                            Aramid fibers (KEVLAR ®)                                                                      1.44      1, 2                                            Mica                2.8       1, 2                                            Calcium metasilicate                                                                              2.9       1, 2                                            Barium sulfate      4.6       1, 2                                            Zinc sulfide        4.1       1, 2                                            Lithopone           4.2-4.3   1, 2                                            Silicates           2.1       1, 2                                            Silicon carbide platelets                                                                         3.18      1, 2                                            Silicon carbide whiskers                                                                          3.2       1, 2                                            Tungsten carbide    15.6      1                                               Diatomaceous earth  2.3       1, 2                                            Polyvinyl chloride  1.41      1, 2                                            Carbonates                                                                    Calcium carbonate   2.71      1, 2                                            Magnesium carbonate 2.20      1, 2                                            Metals and Alloys (powders)                                                   Titanium            4.51      1                                               Tungsten            19.35     1                                               Aluminum            2.70      1                                               Bismuth             9.78      1                                               Nickel              8.90      1                                               Molybdenum          10.2      1                                               Iron                7.86      1                                               Steel               7.8-7.9   1                                               Lead                11.4      1, 2                                            Copper              8.94      1                                               Brass               8.2-8.4   1                                               Boron               2.34      1                                               Boron carbide whiskers                                                                            2.52      1, 2                                            Bronze              8.70-8.74 1                                               Cobalt              8.92      1                                               Beryllium           1.84      1                                               Zinc                7.14      1                                               Tin                 7.31      1                                               Metal Oxides                                                                  Zinc oxide          5.57      1, 2                                            Iron oxide          5.1       1, 2                                            Aluminum oxide      4.0                                                       Titanium oxide      3.9-4.1   1, 2                                            Magnesium oxide     3.3-3.5   1, 2                                            Zirconium oxide     5.73      1, 2                                            Metal Stearates                                                               Zinc stearate       1.09      3, 4                                            Calcium stearate    1.03      3, 4                                            Barium stearate     1.23      3, 4                                            Lithium stearate    1.01      3, 4                                            Magnesium stearate  1.03      3, 4                                            Particulate carbonaceous materials                                            Graphite            1.5-1.8   1, 2                                            Carbon black        1.8       1, 2                                            Natural bitumen     1.2-1.4   1, 2                                            Cotton flock        1.3-1.4   1, 2                                            Cellulose flock     1.15-1.5  1, 2                                            Leather fiber       1.2-1.4   1, 2                                            Micro balloons                                                                Glass               0.15-1.1  1, 2                                            Ceramic             0.2-0.7   1, 2                                            Fly ash             0.6-0.8   1, 2                                            Coupling Agents Adhesion Promoters                                            Titanates           0.95-1.17                                                 Zirconates          0.92-1.11                                                 Silane              0.95-1.2                                                  ______________________________________                                         COMMENTS:                                                                     1 Particularly useful for adjusting density of the cover layer.               2 Particularly useful for adjusting flex modulus of the cover layer.          3 Particularly useful for adjusting mold release of the cover layer.          4 Particularly useful for increasing melt flow of the cover layer.            All fillers except for metal stearates would be expected to reduce the        melt flow index of the cover layer.                                      

The amount of filler employed is primarily a function of weightrequirements and distribution.

Two principal properties involved in golf ball performance areresilience and PGA compression. The resilience or coefficient ofrestitution (COR) of a golf ball is the constant "e," which is the ratioof the relative velocity of an elastic sphere after direct impact tothat before impact. As a result, the COR ("e") can vary from 0 to 1,with 1 being equivalent to a perfectly or completely elastic collisionand 0 being equivalent to a perfectly or completely inelastic collision.

COR, along with additional factors such as club head speed, club headmass, ball weight, ball size and density, spin rate, angle of trajectoryand surface configuration (i.e., dimple pattern and area of dimplecoverage) as well as environmental conditions (e.g. temperature,moisture, atmospheric pressure, wind, etc.) generally determine thedistance a ball will travel when hit. Along this line, the distance agolf ball will travel under controlled environmental conditions is afunction of the speed and mass of the club and size, density andresilience (COR) of the ball and other factors. The initial velocity ofthe club, the mass of the club and the angle of the ball's departure areessentially provided by the golfer upon striking. The factors ordeterminants of particular interest with respect to improved distanceare generally the coefficient of restitution (COR), launch angle, spin,and the surface configuration (dimple pattern, ratio of land area todimple area, etc.) of the ball.

The COR in solid core balls is a function of the composition of the coreand of the cover. The core and/or cover may be comprised of one or morelayers such as in multi-layered balls. In balls containing a wound core(i.e., balls comprising a liquid or solid center, elastic windings, anda cover), the coefficient of restitution is a function of not only thecomposition of the center and cover, but also the composition andtension of the elastomeric windings. As in the solid core balls, thecenter and cover of a wound core ball may also consist of one or morelayers.

The coefficient of restitution is the ratio of the outgoing velocity tothe incoming velocity. In the examples of this application, thecoefficient of restitution of a golf ball was measured by propelling aball horizontally at a speed of 125±5 feet per second (fps) andcorrected to 125 fps against a generally vertical, hard, flat steelplate and measuring the ball's incoming and outgoing velocityelectronically. Speeds were measured with a pair of Oehler Mark 55ballistic screens available from Oehler Research, Inc., P.O. Box 9135,Austin, Tex. 78766, which provide a timing pulse when an object passesthrough 5 them. The screens were separated by 36" and are located 25.25"and 61.25" from the rebound wall. The ball speed was measured by timingthe pulses from screen 1 to screen 2 on the way into the rebound wall(as the average speed of the ball over 36"), and then the exit speed wastimed from screen 2 to screen 1 over the same distance. The rebound wallwas tilted 2 degrees from a vertical plane to allow the ball to reboundslightly downward in order to miss the edge of the cannon that fired it.The rebound wall is solid steel 2.0 inches thick.

As indicated above, the incoming speed should be 125±5 fps but correctedto 125 fps. The correlation, between COR and forward or incoming speedhas been studied and a correction has been made over the ±5 fps range sothat the COR is reported as if the ball had an incoming speed of exactly125.0 fps.

The coefficient of restitution must be carefully controlled in allcommercial golf balls if the ball is to be within the specificationsregulated by the United States Golf Association (U.S.G.A.). As mentionedto some degree above, the U.S.G.A. standards indicate that a"regulation" ball cannot have an initial velocity exceeding 255 feet persecond in an atmosphere of 75° F. when tested on a U.S.G.A. machine.Since the coefficient of restitution of a ball is related to the ball'sinitial velocity, it is highly desirable to produce a ball havingsufficiently high coefficient of restitution to closely approach theU.S.G.A. limit on initial velocity, while having an ample degree ofsoftness (i.e., hardness) to produce enhanced playability (i.e., spin,etc.).

PGA compression is another important property involved in theperformance of a golf ball. The compression of the ball can affect theplayability of the ball on striking and the sound or "click" produced.Similarly, compression can effect the "feel" of the ball (i.e., hard orsoft responsive feel), particularly in chipping and putting.

Moreover, while compression itself has little bearing on the distanceperformance of a ball, compression can affect the playability of theball on striking. The degree of compression of a ball against the clubface and the softness of the cover strongly influences the resultantspin rate. Typically, a softer cover will produce a higher spin ratethan a harder cover. Additionally, a harder core will produce a higherspin rate than a softer core. This is because at impact a hard coreserves to compress the cover of the ball against the face of the club toa much greater degree than a soft core thereby resulting in more "grab"of the ball on the clubface and subsequent higher spin rates. In effectthe cover is squeezed between the relatively incompressible core andclubhead. When a softer core is used, the cover is under much lesscompressive stress than when a harder core is used and therefore doesnot contact the clubface as intimately. This results in lower spinrates.

The term "compression" utilized in the golf ball trade generally definesthe overall deflection that a golf ball undergoes when subjected to acompressive load. For example, PGA compression indicates the amount ofchange in golf ball's shape upon striking. The development of solid coretechnology in two-piece balls has allowed for much more precise controlof compression in comparison to thread wound three-piece balls. This isbecause in the manufacture of solid core balls, the amount of deflectionor deformation is precisely controlled by the chemical formula used inmaking the cores. This differs from wound three-piece balls whereincompression is controlled in part by the winding process of the elasticthread. Thus, two-piece and multilayer solid core balls exhibit muchmore consistent compression readings than balls having wound cores suchas the thread wound three-piece balls.

In the past, PGA compression related to a scale of from 0 to 200 givento a golf ball. The lower the PGA compression value, the softer the feelof the ball upon striking. In practice, tournament quality balls havecompression ratings around 70-110, preferably around 80 to 100.

In determining PGA compression using the 0-200 scale, a standard forceis applied to the external surface of the ball. A ball which exhibits nodeflection (0.0 inches in deflection) is rated 200 and a ball whichdeflects 2/10th of an inch (0.2 inches) is rated 0. Every change of0.001 of an inch in deflection represents a 1 point drop in compression.Consequently, a ball which deflects 0.1 inches (100×0.001 inches) has aPGA compression value of 100 (i.e., 200-100) and a ball which deflects0.110 inches (110×0.001 inches) has a PGA compression of 90 (i.e.,200-110).

In order to assist in the determination of compression, several deviceshave been employed by the industry. For example, PGA compression isdetermined by an apparatus fashioned in the form of a small press withan upper and lower anvil. The upper anvil is at rest against a 200-pounddie spring, and the lower anvil is movable through 0.300 inches by meansof a crank mechanism. In its open position the gap between the anvils is1.780 inches allowing a clearance of 0.100 inches for insertion of theball. As the lower anvil is raised by the crank, it compresses the ballagainst the upper anvil, such compression occurring during the last0.200 inches of stroke of the lower anvil, the ball then loading theupper anvil which in turn loads the spring. The equilibrium point of theupper anvil is measured by a dial micrometer if the anvil is deflectedby the ball more than 0.100 inches (less deflection is simply regardedas zero compression) and the reading on the micrometer dial is referredto as the compression of the ball. In practice, tournament quality ballshave compression ratings around 80 to 100 which means that the upperanvil was deflected a total of 0.120 to 0.100 inches.

An example to determine PGA compression can be shown by utilizing a golfball compression tester produced by Atti Engineering Corporation ofNewark, N.J. The value obtained by this tester relates to an arbitraryvalue expressed by a number which may range from 0 to 100, although avalue of 200 can be measured as indicated by two revolutions of the dialindicator on the apparatus. The value obtained defines the deflectionthat a golf ball undergoes when subjected to compressive loading. TheAtti test apparatus consists of a lower movable platform and an uppermovable spring-loaded anvil. The dial indicator is mounted such that itmeasures the upward movement of the springloaded anvil. The golf ball tobe tested is placed in the lower platform, which is then raised a fixeddistance. The upper portion of the golf ball comes in contact with andexerts a pressure on the springloaded anvil. Depending upon the distanceof the golf ball to be compressed, the upper anvil is forced upwardagainst the spring.

Alternative devices have also been employed to determine compression.For example, Applicant also utilizes a modified Riehle CompressionMachine originally produced by Riehle Bros. Testing Machine Company,Phil., Pa. to evaluate compression of the various components (i.e.,cores, mantle cover balls, finished balls, etc.) of the golf balls. TheRiehle compression device determines deformation in thousandths of aninch under a fixed initialized load of 200 pounds. Using such a device,a Riehle compression of 61 corresponds to a deflection under load of0.061 inches.

Additionally, an approximate relationship between Riehle compression andPGA compression exists for balls of the same size. It has beendetermined by Applicant that Riehle compression corresponds to PGAcompression by the general formula PGA compression =160-Riehlecompression. Consequently, 80 Riehle compression corresponds to 80 PGAcompression, 70 Riehle compression corresponds to 90 PGA compression,and 60 Riehle compression corresponds to 100 PGA compression. Forreporting purposes, Applicant's compression values are usually measuredas Riehle compression and converted to PGA compression.

Furthermore, additional compression devices may also be utilized tomonitor golf ball compression so long as the correlation to PGAcompression is know. These devices have been designed, such as a WhitneyTester, to correlate or correspond to PGA compression through a setrelationship or formula.

The hardness of the cover layers of the golf balls of the invention, andthe compositions and thicknesses of these layers are appropriate toresult in a golf ball having a COR of at least 0.700, more preferably atleast 0.740 and most preferably at least 0.750. The golf ball of theinvention has an overall PGA compression of 40-110, more preferably50-100, and most preferably 60-90.

The inner, intermediate and outer layers together form a cover having athickness of 0.03-0.50 inches, more preferably about 0.050-0.30 inches,and most preferably about 0.10-0.20 inches. The inner and intermediatecover layers each have a thickness of 0.01-0.20 inches, and preferably0.025-0.15 inches. The outer cover layer has a thickness of 0.01-0.20inches, preferably 0.02-0.20 inches in order to accommodate dimples witha depth up to about 0.015 inches, and more preferably 0.025-0.15 inches.In a particularly preferred embodiment, at least one cover layer has athickness of 0.04-0.10 inches. The ratio of the diameter of the ball tothe thickness of the cover, i.e. the sum of the thickness of the innercover layer, intermediate cover layer and outer cover layer, is no morethan about 20:1, preferably no more than about 17:1 and more preferablyno more than about 15:1.

The core of the golf ball preferably is made of a crosslinkedunsaturated elastomer and preferably comprises a thermoset rubber suchas polybutadiene or another diene-containing rubber, but also can bemade of other core materials which provide sufficient COR. For example,the core can be wound, or can be a non-wound single or multi-layer corecontaining a solid thermoplastic or thermoset ionomeric or non-ionomericpolyolefin, polyurethane, polyamide, polyester, dynamically vulcanizedrubber, etc., or blend thereof. The diameter of the core is determinedbased upon the desired overall ball diameter, minus the combinedthicknesses of the inner, intermediate and outer cover layers. The CORof the core is appropriate to impart to the finished golf ball a COR ofat least 0.700, and preferably at least 0.750. The core typically, butnot necessarily, has a diameter of about 0.80-1.62 inches, preferably1.2-1.6 inches, a PGA compression of 10-90, more preferably 20-80 andmost preferably 20-70. The golf ball preferably has a COR in the rangeof 0.600-0.850.

Conventional solid cores are typically compression molded from 20 a slugof uncured or lightly cured elastomer composition comprising a high ciscontent polybutadiene and a metal salt of an α, β, ethylenicallyunsaturated carboxylic acid such as zinc mono or diacrylate ormethacrylate. To achieve higher coefficients of restitution in the core,the manufacturer may include fillers such as small amounts of a metaloxide such as zinc oxide. In addition, larger amounts of metal oxidethan those that are needed to achieve the desired coefficient are oftenincluded in conventional cores in order to increase the core weight sothat the finished ball more closely approaches the U.S.G.A. upper weightlimit of 1.620 ounces. Other materials may be used in the corecomposition including compatible rubbers or ionomers, and low molecularweight fatty acids such as stearic acid. Free radical initiators such asperoxides are admixed with the core composition so that on theapplication of heat and pressure, a complex curing cross-linkingreaction takes place.

The cover layers can be formed over the cores by injection molding,compression molding, casting or other conventional molding techniques,or by vacuum forming, spraying, dipping, etc. Each layer preferably isseparately formed. It is preferable to form each layer by eitherinjection molding or compression molding. A more preferred method ofmaking the golf ball of the invention is to successively injection moldin three separate molds. First, the inner cover layer is injectionmolded over the core in a smooth cavity mold, subsequently theintermediate cover layer is injection molded over the inner cover layerin a smooth cavity mold, and finally the outer cover layer is injectionmolded over the intermediate cover layer in a dimpled cavity mold.

As indicated above, soft cover layers have a Shore D hardness in therange of 10-55 and preferably 30-50 when the hardness is measured on thecurved surface of a molded cover. In a particularly preferred embodimentof the invention the soft cover layer or layers have a Shore D hardnessin the range of 40-50. To form one preferred embodiment of a soft coverlayer for use as an inner, intermediate or outer cover layer, one ormore low modulus ionomers (i.e., soft ionomers), or a blend of one ormore high modulus ionomers (i.e., hard ionomers) and one or more lowmodulus ionomers (i.e., soft ionomers) in a mixture can be used. A highmodulus ionomer is one which has a flexural modulus of about15,000-120,000 psi or more as measured under ASTM method D-790. Thehardness of this type of ionomer is at least 50 on the Shore D scale asmeasured on a plaque, rather than on a ball, in accordance with ASTMmethod D-2240. Typically, hard ionomers are copolymers with two types ofmonomers. A low modulus ionomer which can be blended with the highmodulus ionomer to form the inner layer has a flexural modulus of about1,000 to about 15,000 psi (ASTM D-790), and a hardness as measured on aplaque of about 10-40 on the Shore D scale (ASTM D-2240). Typically,soft ionomers are terpolymers.

To form a cover layer of intermediate hardness, hard and soft covermaterials typically are blended in a ratio of 25-75 wt % hard(copolymer) ionomer and 75-25 wt % soft (terpolymer type) ionomer.Alternatively, cover layers of intermediate hardness as well as softcover layers can be comprised of a single ionomer having a hardness thatmeets the requirements of Shore D hardness, i.e., a Shore D hardness of10-55 for a soft cover layer and 50-65 for a cover layer of intermediatehardness.

To form a hard cover layer, one or more hard (high modulus) ionomers areused. Furthermore, low modulus ionomers can be blended with the highmodulus ionomer or ionomers to improve compressing, toughness at lowtemperatures, enhanced feel, scuff resistance, etc., as long as theShore D hardness requirements for the hard cover layer are met.

The hard ionomer resins include ionic copolymers which are the e.g.sodium, zinc, magnesium, calcium, manganese, nickel, potassium orlithium, etc. salt, or blend thereof, of the reaction product of anolefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylicacid having from 3 to 8 carbon atoms and which result in a ball havingthe desired combination of COR, compression, and inner cover layerhardness. The carboxylic acid groups of the copolymer are partiallyneutralized by the metal ions, i.e., about 10-100%, typically about10-75% and more preferably about 30-70% neutralized. The hard ionomericresins typically are copolymers of ethylene with acrylic and/ormethacrylic acid. Two or more hard ionomer resins can be blended.

The metal cation salts utilized in the invention are those salts whichprovide the metal cations capable of neutralizing, to various extents,the carboxylic acid groups of the high acid copolymer. These includeacetate, oxide or hydroxide salts of e.g. lithium, calcium, zinc,sodium, potassium, nickel, magnesium, and manganese, etc.

Examples of such lithium ion sources are lithium hydroxide monohydrate,lithium hydroxide, lithium oxide and lithium acetate. Sources for thecalcium ion include calcium hydroxide, calcium acetate and calciumoxide. Suitable zinc ion sources are zinc acetate dihydrate and zincacetate, a blend of zinc oxide and acetic acid. Examples of sodium ionsources are sodium hydroxide and sodium acetate. Sources for thepotassium ion include potassium hydroxide and potassium acetate.Suitable nickel ion sources are nickel acetate, nickel oxide and nickelhydroxide. Sources of magnesium include magnesium oxide, magnesiumhydroxide and magnesium acetate. Sources of manganese include manganeseacetate and manganese oxide.

Non-limiting examples of commercially available hard ionomeric resinswith intermediate acid levels which can be used in a blend to form thecover layers include the hard sodium ionic copolymer sold under thetrademark Surlyn®8940 and the hard zinc ionic copolymer sold under thetrademark Surlyn®9910. Surlyn®8940 is a copolymer of ethylene withmethacrylic acid with about 15 weight % acid which is about 29%neutralized with sodium ions. This resin has an average melt flow indexof about 2.8. Surlyn®9910 is a copolymer of ethylene and methacrylicacid with about 15 weight % acid which is about 58% neutralized withzinc ions. The average melt flow index of Surlyn®9910 is about 0.7.Additional examples include lotek 1002, lotek 1003, lotek 8000, lotek8020, lotek 8030, lotek 7010 and lotek 7030 which are sold by ExxonCorporation. Non-limiting examples of ionomeric resins with intermediateacid levels are shown below on Table 3.

Hard cover layers and other cover layers containing hard-soft blendsalso can be made using high acid ionomer resins. High acid ionomerresins preferably contain more than 16% by weight of a carboxylic acid,preferably 17-25% by weight of a carboxylic acid, and most preferablyabout 18.5-21.5% by weight of a carboxylic acid. Examples of a number ofcopolymers suitable for use to produce the high acid ionomers include,but are not limited to, high acid embodiments of an ethylene/acrylicacid copolymer, an ethylene/methacrylic acid copolymer, anethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer, anethylene/methacrylic acid/vinyl acetate copolymer, an ethylene/acrylicacid/vinyl alcohol copolymer, etc. The base copolymer broadly containsgreater than 16% by weight unsaturated carboxylic acid, from about 30 toabout 83% by weight ethylene and from 0 to about 40% by weight of asoftening comonomer. Preferably, the copolymer contains about 20% byweight unsaturated carboxylic acid and about 80% by weight ethylene.Most preferably, the copolymer contains about 20% acrylic acid with theremainder being ethylene. Examples of commercially available high acidmethacrylic acid-based ionomers which can be used in accordance with theinvention include Surlyn® AD-8422 (sodium cation), Surlyn® 8162 (zinccation), Surlyn® SEP-503-1 (zinc cation), and Surlyn® SEP-503-2(magnesium cation). According to DuPont, all of these ionomers containfrom about 18.5 to about 21% by weight methacrylic acid.

A cover layer with a particular Shore D hardness can be formed using asingle ionomer, or more commonly, a blend of two or more ionomers.Non-limiting examples of ionomers which can be used to form golf ballcovers are as follows:

                                      TABLE 3                                     __________________________________________________________________________    Typical Properties of Some Commercially Available                             Hard Surlyn ® Resins                                                                        8940                                                                              9910                                                                              8920                                                                              8528                                                                              9970                                                                             9730                                                       Cation type                                                              ASTM D                                                                             Sodium                                                                            Zinc                                                                              Sodium                                                                            Sodium                                                                            Zinc                                                                             Zinc                                     __________________________________________________________________________    Melt flow index, gms/10 min.                                                               D-1238                                                                             2.8 0.7 0.9 1.3 14.0                                                                             1.6                                      Specific gravity, g/cm.sup.3                                                               D-792                                                                              0.95                                                                              0.97                                                                              0.95                                                                              0.94                                                                              0.95                                                                             0.95                                     Hardness, Shore D                                                                          D-2240                                                                             65  64  66  60  62 63                                       Tensile strength,                                                             (kpsi)       D-638                                                                              (4.8)                                                                             (3.6)                                                                             (5.4)                                                                             (4.2)                                                                             (3.2)                                                                            (4.1)                                    MPa               33.1                                                                              24.8                                                                              37.2                                                                              29.0                                                                              22.1                                                                             28.3                                     Elongation, %                                                                              D-638                                                                              470 290 350 450 460                                                                              460                                      Flexural Modulus,                                                             (kpsi)       D-790                                                                               (51)                                                                              (48)                                                                              (55)                                                                              (32)                                                                              (28)                                                                             (30)                                    MPa               350 330 380 220 190                                                                              210                                      Tensile Impact (23° C.),                                               KJ/m.sup.2   D-1822S                                                                            1020                                                                              1020                                                                              865 1160                                                                              760                                                                              1240                                     (ft-lbs./in.sup.2)                                                                              (485)                                                                             (485)                                                                             (410)                                                                             (550)                                                                             (360)                                                                            (590)                                    Vicat temperature, ° C.                                                             D-1525                                                                              63  62  58  73  61                                                                               73                                      __________________________________________________________________________

                  TABLE 4                                                         ______________________________________                                        Properties of Additional Hard Surlyn ® Resins                                            SURLYN ®                                                                            SURLYN ®                                                                            SURLYN ®                               IONOMER        8920      8140      9120                                       ______________________________________                                        Cation             Na        Na      Zn                                       Melt Flow                                                                              gms/10 min.                                                                             0.9       2.6     1.3                                      Index                                                                         MP       ° C.                                                                             84        88      85                                       FP       ° C.                                                                             52        49      50                                       Tensile  kpsi.     5.4       5.0     3.8                                      Strength                                                                      Yield Strength                                                                         kpsi      2.2       2.8     2.4                                      Elongation                                                                             %         350       340     280                                      Flex Modulus                                                                           kpsi      55        71      64                                       Shore D            66        70      69                                       Hardness                                                                      ______________________________________                                    

                                      TABLE 5                                     __________________________________________________________________________    Typical Properties of Iotek Ionomers                                                              7010                                                                             7020                                                                             7030                                                                             8000                                                                              8020                                                                              8030                                                ASTM     Cation type                                               Resin Properties                                                                         Method                                                                            Units                                                                              zinc                                                                             zinc                                                                             zinc                                                                             sodium                                                                            sodium                                                                            sodium                                   __________________________________________________________________________    Melt Index D-1238                                                                            g/10 min                                                                           0.8                                                                              1.5                                                                              2.5                                                                              0.8 1.6 2.8                                      Density    D-1505                                                                            kg/m.sup.3                                                                         968                                                                              966                                                                              964                                                                              957 956 956                                      Melting Point                                                                            D-3417                                                                            ° C.                                                                        83.5                                                                             84 85 83  84  87                                       Crystallization Point                                                                    D-3417                                                                            ° C.                                                                        55 56 58 45  47  49                                       Vicat Softening Point                                                                    D-1525                                                                            ° C.                                                                        60 60 60 54  54.5                                                                              55.5                                     Tensile strength at break                                                                D-638                                                                             MPa  24.5                                                                             23.5                                                                             22.6                                                                             33  32.5                                                                              32                                       Yield strength                                                                           D-638                                                                             MPa  14 13 12 19  18.5                                                                              18                                       Elongation at break                                                                      D-638                                                                             %    440                                                                              450                                                                              460                                                                              370 380 410                                      1% Secant modulus                                                                        D-638                                                                             MPa  150                                                                              135                                                                              125                                                                              280 280 280                                      Shore Hardness D                                                                         D-2240                                                                            --   54 53 52 60  60  60                                       Flex modulus (3 mm)                                                                      D-790                                                                             MPa  190                                                                              175                                                                              155                                                                              320 340 355                                      __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        Example of Exxon High Molecular Weight ionomers                               PROPERTY  Ex 1005 Ex 1006 Ex 1007                                                                             Ex 1008                                                                             Ex 1009                                                                             7310                              ______________________________________                                        Melt Index,                                                                             0.7     1.3     1.0   1.4   0.8   1.0                               g/10 min.                                                                     Cation    Na      Na      Zn    Zn    Na    Zn                                Melting   85.3    86      85.8  86    91.3  91                                Point, ° C.                                                            Vicat     54      57      60.5  60    56    69                                Softening                                                                     Point, ° C.                                                            Tensile @ 33.9    33.5    24.1  23.6  32.4  24                                Break, MPa                                                                    Elongation @                                                                            403     421     472   427   473   520                               Break, %                                                                      Hardness, 58      58      51    50    56    52                                Shore D                                                                       Flexural  289     290     152   141   282   150                               Modulus, MPa                                                                  ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        Exxon High Acid Ionomers                                                                               ESCOR ®      ESCOR ®                                    Ex     Ex     (IOTEK)                                                                              Ex   Ex   (IOTEK)                             Property   1001   1002   959    1003 1004 960                                 ______________________________________                                        Melt Index, g/10                                                                         1.0    1.6    2.1    1.1  2.0  1.8                                 min.                                                                          Cation     Na     Na     Na     Zn   Zn   Zn                                  Melting Point, ° C.                                                               83.7   83.7   --     82   82.5 79                                  Vicat Softening                                                                          51.5   51.5   58     56   55   55                                  Point, ° C.                                                            Tensile @ Break                                                                          34.4   31.7   34     24.8 20.6 24                                             MPa    MPa    MPa    MPa  MPa  MPa                                 Elongation @                                                                             341    348    280    387  437  430                                 Break, %                                                                      Hardness, Shore D                                                                        63     62     65     54   53   57                                  Flexural Modulus                                                                         365    380    480    147  130  170                                            MPa    MPa    MPa    MPa  MPa  MPa                                 ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        Additional Exxon High Acid Ionomers                                           Property    Unit     EX 989  EX 993                                                                              EX 994                                                                              EX 990                               ______________________________________                                        Melt Index  g/10 min.                                                                              1.30    1.25  1.32  1.24                                 Moisture    ppm      482     214   997   654                                  Cation Type --       Na      Li    K     Zn                                   M+ content by AAS                                                                         wt. %    2.74    0.87  4.54  0                                    Zn content by AAS                                                                         wt. %    0       0     0     3.16                                 Density     kg/m.sup.3                                                                             959     945   976   977                                  Vicat softening point                                                                     ° C.                                                                            52.5    51    50    55.0                                 Crystallization point                                                                     ° C.                                                                            40.1    39.8  44.9  54.4                                 Melting point                                                                             ° C.                                                                            82.6    81.0  80.4  81.0                                 Tensile at yield                                                                          MPa      23.8    24.6  22    16.5                                 Tensile at break                                                                          MPa      32.3    31.1  29.7  23.8                                 Elongation at break                                                                       %        330     260   340   357                                  1% secant modulus                                                                         MPa      389     379   312   205                                  Flexural modulus                                                                          MPa      340     368   303   183                                  Abrasion resistance                                                                       mg       20.0    9.2   15.2  20.5                                 Hardness Shore D                                                                          --       62      62.5  61    56                                   Zwick Rebound                                                                             %        61      63    59    48                                   ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Zinc-Based Iotek Terpolymer Ionomers                                          Property    Unit       IOTEK 7520                                                                              IOTEK 7510                                   ______________________________________                                        Melt Index  g/10 min.  2.0       0.8                                          Density     g/cc       0.96      0.97                                         Melting Point                                                                             ° F.                                                                              151       149                                          Vicat Softening Point                                                                     ° F.                                                                              108       109                                          Flex Modulus                                                                              psi        3800      5300                                         Tensile Strength                                                                          psi        1450      1750                                         Elongation  %          760       690                                          Hardness, Shore D                                                                         --         32        35                                           ______________________________________                                    

As indicated above, ionomers which contain softening comonomers, such asionomeric terpolymers, can be included in the cover layers. Non-limitingexamples of a softening comonomer include vinyl esters of aliphaticcarboxylic acids wherein the acids have 2 to 10 carbon atoms, vinylethers wherein the alkyl group contains 1 to 10 carbon atoms, and alkylacrylates or methacrylates wherein the alkyl group contains 1 to 10carbon atoms. Suitable softening comonomers include vinyl acetate,methyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate, butyl methacrylate, or the like.

Non-limiting examples of soft ionomers to be blended with theabove-described hard ionomers to form the cover layers of the inventivegolf ball comprise sodium, zinc magnesium, calcium, manganese, nickel,potassium or lithium, etc. salts of a terpolymer of an olefin havingfrom about 2 to 8 carbon atoms, acrylic acid or methacrylic acid, and asoftening comonomer which is an unsaturated monomer of the acrylateester class having from 1 to 21 carbon atoms. The soft ionomer ispreferably an ionomer made from an acrylic acid-based polymer and anunsaturated monomer of the acrylate ester class. The soft ionomerstypically have an acid content of 3-12 wt % (including the weightpercent of the softening comonomer).

It has been determined that when hard-soft ionomer blends are used forcover layers, good results are achieved when the relative combination isin a range of about 90 to about 10 wt % hard ionomer and about 10 toabout 90 wt % soft ionomer. For cover layers which are soft or ofintermediate hardness, results are improved by adjusting the range toabout 75 to 25 wt % hard ionomer and 25 to 75 wt % soft ionomer. Evenbetter results are noted at relative ranges of about 60 to 40 wt % hardionomer resin and about 40 to 60 wt % soft ionomer resin. For hard coverlayers, the wt % of soft ionomer preferably will not exceed about 25 wt%.

As indicated above, the cover layers optionally may include hardening orsoftening modifiers, non-limiting examples of which include a metalstearate, such as zinc stearate, or another fatty acid salt, asdescribed in commonly assigned U.S. Pat. Nos. 5,306,760 and 5,312,857.One purpose of the metal stearate or other fatty acid salt is to reducethe cost of production of the ball without affecting overall performanceof the finished ball. Furthermore, polar-group modified rubbers can beblended with ionomers as described, for example, in commonly assignedU.S. Pat. Nos. 4,986,545, 5,098,105, 5,330,837 and 5,338,610.Thermoplastic elastomers which act as hardening or softening agents,including polyurethane, a polyester elastomer such as that sold byDuPont as HYTREL®, a polyester polyurethane such as B.F. GoodrichCompany's ESTANE® polyester polyurethane X-4517, and a polyester amidesuch as that sold by Elf Atochem S.A. under the name PEBAX®, can beadded. A plastomer such as that sold by Exxon under the name EXACT™,e.g., EXACT™ 4049 can be included. Various plasticizers and processingaids also can be used.

The golf balls of the present invention typically are coated with athin, glossy, protective topcoat of polyurethane, epoxy, or anothersuitable topcoat material. The topcoat generally has a thickness in therange of 0.0005 to 0.005 inches, and more preferably 0.001 to 0.002inches. To provide for good adhesion of the top coat on the outer coverlayer, a primer coat typically is included between the outer cover layerand top coat. This primer coat generally also is made of polyurethane orepoxy, and typically has a thickness after curing of 0.0001 to 0.0015inches, and more preferably 0.00025-0.001 inches.

When the golf ball of the invention has more than three cover layers,the inner cover layer as defined in this application can be formed fromtwo or more layers which, taken together, meet the requirements ofhardness and thickness of the layer or layers which are defined hereinas the inner cover layer. Similarly, the intermediate cover layer can beformed from two or more layers which, taken together, meet therequirements of hardness and thickness of the layer or layers which aredefined herein as the intermediate cover layer. The outer cover layercan be formed from two or more layers which, taken together, meet therequirements of hardness and thickness of the layer or layers which aredefined herein as the outer cover layer. Furthermore, one or moreadditional, thin ionomeric or non-ionomeric layers can be added oneither side of the inner cover layer and intermediate cover layer aslong as the objectives of the invention are achieved.

Having generally described the invention, the following examples areincluded for purposes of illustration so that the invention may be morereadily understood and are in no way intended to limit the scope of theinvention unless otherwise specifically indicated.

EXAMPLE 1

A number of golf ball cores were formed using the core formulation shownbelow:

    ______________________________________                                        Material        Parts by Weight                                               ______________________________________                                        First polybutadiene.sup.2                                                                     70                                                            Second polybutadiene.sup.3                                                                    30                                                            Zinc oxide.sup.4                                                                              43                                                            Regrind.sup.5   20                                                            Zinc diacrylate.sup.6                                                                         20                                                            Zinc stearate.sup.7                                                                           15                                                            Peroxide.sup.8  0.9                                                           ______________________________________                                         .sup.1 Cariflex BR1220, Meuhlstein, Norwalk, CT                               .sup.3 Taktene 220, Bayer Corp., Akron, OH                                    .sup.4 Zinc Corp. of America, Monaca, PA                                      .sup.5 Golf ball core regrind (internal source)                               .sup.6 Rockland React Rite, Rockland, CA                                      .sup.7 Synpro, Cleveland, OH                                                  .sup.8 Luperco 231 XL, R. T. Vanderbilt, Norwalk, CT                     

The formulation was used to make a number of 1.38 inch cores usingcompression molding and curing at 320° F. for 5-20 minutes. The coreswere molded to a size of 1.38 inches using 1.40 inch cavities in the MTSform.

Hemispheres for the inner cover layer were formed by injection molding.The inner cover layers were compression molded over the core using 1.50inch compression molding cavities. The compression molding cycle wasfive minutes at 320° F. followed by nine minutes of cooling at 600 psi.

An intermediate cover layer was injection molded over the inner coverlayer using a 1.57 inch smooth cavity injection mold.

An outer cover layer was injection molded over the intermediate coverlayer for each ball using a six cavity mold to form golf balls having afinal ball size of 1.68 inches. The balls were finished usingconventional finishing techniques. The properties of the golf balls andformulations for the covers are shown below on Table 10.

EXAMPLE 2-4

The procedure of Example 1 was repeated using different combinations ofcover layers at the same cover layer thicknesses. The results are shownon Table 10.

COMPARATIVE EXAMPLES A-B

A golf ball core was formed having the properties shown below on Table3. The core had a diameter of 1.47 inches. An inner cover layer ofionomer was injection molded over the core, followed by an outer coverlayer of ionomer, which also was injection molded. The ionomericcompositions of the inner cover layer and outer cover layer are shown onTable 10.

Two additional types of golf balls with double covers were formed. Theproperties and composition of the two additional types of golf balls isshown on Table 10.

COMPARATIVE EXAMPLE C

A golf ball core was formed having the properties shown below. A singlecover layer was injection molded over the core. The composition of thecover, along with the properties of the resulting ball, are shown onTable 10.

The three cover layer balls of Examples 1-4 provide for a favorablebalance of spin and feel characteristics. Looking at Examples 1 and 2 inconjunction with Comparative Example A, it is noted that the balls ofComparative Example A have inferior feel and softness as compared to theballs of Examples 1 and 2, as is evidenced by the higher PGA compressionof the balls of Comparative Example A as compared to the balls ofExamples 1 and 2. While the ball of Comparative Example B has areasonably good combination of spin and feel, the ball of Example 3 ispreferred when somewhat lower spin is desired. The lower spin of theball of Example 3 may offer longer roll upon landing and betterstability in windy conditions, with the ball being less likely toupshoot. The balls of Example 4 have higher spin than those ofComparative Example B, which may be desirable to a player with a slow orintermediate swing speed who desires sufficient backspin to stop a golfball on a green, for example. A high spin golf ball such as that ofExample 4 also is useful for a player who would like high spin on shortshots. Thus, the golf balls of Example 4 are superior to those ofComparative Example B when very high spin is desired. The ball ofComparative Example C has excessively high spin on all shots, andtherefore would not provide good distance on drives and would not beuseful to result in "variable spin properties" such as high spin onshort shots and low spin on long shots.

As will be apparent to persons skilled in the art, various modificationsand adaptations of the structure above described will become readilyapparent without departure from the spirit and scope of the invention,the scope of which is defined in the appended claims.

                  TABLE 10                                                        ______________________________________                                                                       Comp. Comp. Comp.                              Ex. 1      Ex. 2  Ex. 3  Ex. 4 A     B     C                                  ______________________________________                                        Core                                                                          Size    1.38   1.38   1.38 1.38  1.47  1.47  1.545                            Weight  28     28     28   28    32.9  32.9  36.7                             PGA Comp                                                                              55     55     55   55    54    54    73                               COR     756    756    756  756   762   762   778                              Shore C/D                                                                             80/49  80/49  80/49                                                                              80/49 78/47 78/47 81/47                            Inner Mantle                                 None                             Materials                                                                             pph    pph    pph  pph   pph   pph                                    Iotek 1002                                                                            --     50     --   50    50    50    --                               Iotek 1003                                                                            --     50     --   50    50    50    --                               Iotek 7510                                                                            50     --     50   --    --    --    --                               Iotek 7520                                                                            50     --     50   --    --    --    --                               Size    1.47   1.47   1.47 1.47  1.57  1.57  --                               Thickness                                                                             0.045  0.045  0.045                                                                              0.045 0.050 0.050 --                               Weight  33.5   33.5   33.5 33.5  38.4  38.4  --                               PGA Comp                                                                              54     75     54   75    78    78    --                               COR     750    790    750  790   795   795   --                               Shore C/D                                                                             70/47  97/71  70/47                                                                              97/71 97/71 97/71 --                               Intermediate                     None  None  None                             Mantle                                                                        Materials                                                                             pph    pph    pph  pph                                                Iotek 1002                                                                            25     --     50   25    --    --    --                               Iotek 1003                                                                            25     --     50   25    --    --    --                               Iotek 7510                                                                            25     50     --   25    --    --    --                               Iotek 7520                                                                            25     50     --   25    --    --    --                               Size    1.57   1.57   1.57 1.57  --    --    --                               Thickness                                                                             0.050  0.050  0.050                                                                              0.050 --    --    --                               Weight  38.6   38.7   38.6 38.6  --    --    --                               PGA Comp                                                                              66     81     72   86    --    --    --                               COR     753    774    773  780   --    --    --                               Shore C/D                                                                             82/58  70/47  97/71                                                                              82/58 --    --    --                               Finished Ball                                                                 Cover   pph    pph    pph  pph   pph   pph   pph                              Materials                                                                     Iotek 1002                                                                            45.3   45.3   --   --    45.3  --    --                               Iotek 1003                                                                            45.3   45.3   --   --    45.3  --    --                               Iotek 7510                                                                            --     --     45.3 45.3  --    45.3  45.3                             Iotek 7520                                                                            --     --     45.3 45.3  --    45.3  45.3                             TG MB   9.4    9.4    9.4  9.4   9.4   9.4   9.4                              Thickness                                                                             0.055  0.055  0.055                                                                              0.055 0.055 0.055 0.070                            Weight  46     46     46.1 46    46.2  46.2  45.8                             PGA Comp                                                                              85     95     78   90    99    82    79                               COR     779    789    762  768   817   777   772                              Shore C/D                                                                             97/71  97/71  70/47                                                                              70/47 97/71 70/47 70/47                            Spin *1 7857   7568   9028 10018 7957  9278  10309                            Spin Std.                                                                             504    614    298  376   607   129   216                              Dev.                                                                          ______________________________________                                         *1  Spin test  TF 9 iron at 105 fps, Strata Tour 90 control > 9029 (200       Std. Dev.), Titleist Tour Balata 100 > 9495 (238 Std. Dev.)              

What is claimed is:
 1. A golf ball, comprising:a solid or wound core,and a multi-layer cover having at least three separate and distinctlayers, said multi-layer cover comprisingan inner cover layer formedaround the core, an intermediate cover layer formed around the innercover layer, and an outer cover layer formed around the intermediatecover layer, each cover layer having a different Shore D hardness thaneach adjacent cover layer, the intermediate layer having a Shore Dhardness softer than the inner cover layer and harder than the outercover layer.
 2. A golf ball according to claim 1, wherein theintermediate cover layer is at least 3 Shore D points softer than boththe inner and outer cover layers.
 3. A golf ball, comprising:a solid orwound core, and a multi-layer cover having at least three separate anddistinct layers, said multi-layer cover comprisingan inner cover layerformed around the core, the inner cover layer having a Shore D harnessof at least 62, an intermediate cover layer formed around the innercover layer, and an outer cover layer formed around the intermediatecover layer, each cover layer having a different Shore D hardness thaneach adjacent cover layer, the intermediate layer having a Shore Dhardness softer than the inner cover layer and harder than the outercover layer.
 4. A golf ball according to claim 3, wherein theintermediate cover layer has a Shore D hardness in the range of 50-65and the outer cover layer has a Shore D hardness in the range of 10-55and is softer than the intermediate cover layer.
 5. A golf ballaccording to claim 3, wherein the intermediate cover layer is harderthan the outer cover layer.
 6. A golf ball comprising:a solid core, anda multi-layer cover having at least three separate and distinct layers,said multi-layer cover comprisingan inner cover layer comprising atleast one member selected from the group consisting of ionomers,thermoplastic elastomers and non-ionomeric polyolefins, an intermediatecover layer comprising at least one member selected from the groupconsisting of ionomers, thermoplastic elastomers and non-ionomericpolyolefins, and an outer cover layer comprising at least one memberselected from the group consisting of ionomers, thermoplastic elastomersand non-ionomeric polyolefins, wherein each of the inner cover layer,intermediate cover layer and outer cover layer is a separate layer andthe intermediate layer has a Shore D hardness softer than the innercover layer and harder than the outer cover layer.